Marker light for airports



Feb. 20, 1940. E. M. GLAS OW 2,191,319

MARKER LIGHT AIRPORTS 2 Sheets-Sheet 1 a 4 a \\V fl 6 d Z 7 7 C A 5 m fi 3 l 2 m Z w T v R INVENTOR ERNEST M. GLASGOW B Y IIS ATTORNEYS Feb. 20, 1940.

E. M. GLASGOW- MARKER LIGHT FOR AIRPORTS Filed Feb. 16, 19:58 2 Sheets- Sheet 2 INVENTOR ERNEST M. GLASGOW 1BY HIS ATTORNEYS Patented Feb. 20} 1940.

' UNITED STATES 2,191,315 mm mm FOR AIRPORTS Ernest M. Glasgow, 'lovmco, N. 1., alsignor to Russell & Stoll Company, Inc., New York, N. Y., a corporation of New York Application February 16, 1938, Serial No. 190,845

8 Claims. (01. 240-13) This invention'relates to marker lights for airports, and has for its main object to provide a device of this character which permits the incandescent lamp filament or other source of light to be mounted below the surface of the landing field, andwhich reflects the light therefrom to a focus thereabove, and radiates the light from said focus in all directions at a predetermined acute upward angle to the surface of the landing field.

In this marker light, visibility is of primary importance as distinguished from illumination, because the light is essentially a beacon for guiding pilots of approaching planes to the landing field, and indicating the ,extent thereof. The illumination of the field may be provided by other means such as flood lights, although the present invention provides some local illumination of the field as a matter of secondary importance.

Another object'is' to reduce the projection of the marker light above the ground surface, to avoid obstruction to passage of the airplane landing wheels.

A further object is to eliminate castingof shadowsby structure supporting the cover of the marker light.

Other objects and features of novelty will be apparent as the following description proceeds, referring to the accompanying drawings, in which 1 Figure 1 is a vertical section through the marker light according to the present invention, taken along the line of Figure 2;

Figure 2 is a top plan view of the marker light shown in Figure 1, part of the cover being broken away to show the parts therebelow in section; an

Figure 3 is a luminosity curve in polar coordinates, in which the radii are lumens and the angles are degrees above the horizontal.

The marker light comprises a casing having a lower portion 4 which is adapted to be sunkinto the ground, and a cover 5 whi h projects above the ground surface. The Iowa or" well portion 4 has an annular flange 6 which rests upon the ground surface. The bottom of the casing part 4 comprises a centrally apertured flange I which is bolted to a wiring chamber or junction box 8 which receivesthe underground conduit through which the electric current is supplied.

Within the lower casing part 4 a lamp socket 9 is mounted on the flange I, the socket 9 being wired and connected to the conductors of the conduit 8 in any desired manner, through the tion.

-tutes the base of the cover.

aperture in the bottom I. An incandescent lamp bulb I is mounted in the socket 9.

Surrounding the filament of the lamp bulb i0 is an internalrefiector ll having the surface of an ellipsoid of revolution. The reflector I l' is supported within the lower casing. part 4 in any suitable manner, for example by brackets l2 secured by screws l3,

The cover' 5 carries an external reflector 15, the surface of which is a paraboloid of re'volu- 10 In the form shown the reflector l5 is supported by a'post l6 having threaded engagement with a central boss ll of the cover 5. A machined head or nut l8 has threaded engagement"- with the posts l6 to support the reflector there above, the machined bolt l8 and the metal reflector together constituting the parabolic sur- -face. The outer part of the refiector l i'is modified in shape, being generated by the arc of acircle. 20 1 The cover 5 is supported by radially arrange posts 2| which as shown in Figure 2, are stream- 7 lined in the radial direction. These posts extend down to an annular flange 22 which consti- Inside of the series of posts 2| is mounted an annular lens 23, through which all of the light from the marker passes outwardly. The lens 23 is retained in place by a ring 24 having threaded engagement with the base flange 22. Suitable water-tight 80 gasket means are provided above and below the lens 23. The base flange 22 of the cover is bolted .to the annular flange 6 of the lower casing part by bolts 25, suitable gasket means being interposed therebetween. g

In operation, the annular reflector ll being an ellipsoid of revolution and the filament of the lamp bulb being located at one focus of the ellipse, all of the reflected light is concentrated at the other focus of the ellipse at the point A 40 shown in the drawings. However, as the lamp filament has appreciable dimensions, and a ring filament is preferred, the ellipse which generates the surface of revolution has its major axis inclined. Hence while one focus of the ellipse is at 5 the point A, which lies in the axis of revolution,

the other focus B of the ellipse is displaced from the axis of revolution, so that the major axis of the ellipse is inclined. As the ring filament is located at this focus the line B 0 represents the projection of the ring filament. The parabolic surface I! is generated by a parabola which also has its focus at the point A. The axis of the parabola, however, is inclined upward at a predetermined angle. Inasmuch as all of the reflected light from the ellipsoid is concentrated at the focus A which is also the focus of the paraboloid, all of the light from the focus A will be reflected by the paraboloid surface in rays parallel to the predetermined angle at which its axis is inclined. This angle is preferably 1 1 degrees, but it is obvious that a greater or lesser angle may be provided as desired.

In addition to the reflected light from the ellipsoidal. surface, the disposition of which is described above, it should be noted that there are direct rays from the lamp filament which engage the surfaces l5 and 20. The surface 20, which is generated by a circular arc, servesto reflect such direct rays downwardly and outwardly onto the adjacent surface of the landing field, for

localillumination. The direct rays from the fllament which engage the parabolic surface 15 are reflected onto an annular reflector "which surrounds the ellipsoidal reflector II. This annular reflector 28 redirects these spill rays upwardly and outwardly through the lens 23.

It should be noted, as shown in Figure 2, that the lens 23 is of greater thickness adjacent the posts2l than its thickness. at points therebe tween. In the preferred form shown the outer surface of the lens 23 is a circle while the inner long as the sharper curvature of the inner sur;

face is maintained to provide the desired refraction eflfect. y

The foregoing description has been directed to the use of the invention asan airport marker li'ght,-but it is obvious that it is adapted for analogous uses, such for ,example as under water lighting for swimming pools, fountains and the like. In these, where illumination is more important than visibility, the reflector 20 may constitute the greater, and the parabolic part I5 the lesser part of the combined external reflector, if desired.

While the preferred embodiment of the invention has been described in detail, it is to be understood that the invention is not limited to these details, but insteadembraces such embodiments of the broad idea as fall within thescope o the appended claims.

I claim: I

1. In a marker light containing a source from which light is reflected radially, a cover, annularly spaced posts supporting said cover, and means for eliminating shadows cast by said posts comprising a refractor adapted to direct said light rays around said posts.

2. In a marker light containing a source from which light is reflected radially, acover, annularly spaced posts supporting said cover, and means for eliminatingshadows cast, by said posts comprising a refractor adapted to direct said light rays around said posts, said refractor comprising lens means having diminishing thickness between said posts, and greater thickness adjacent said posts.

3. A marker light in which light from a source is reflected outwardly in all directions at a predetermined angle from a ground plane, compris ing an ellipsoidal reflecting surface combined directing reflected light therefrom to a focus, a

paraboloidal reflecting surface having the same focus, and an annular reflecting surface surrounding said ellipsoidal surface for reflecting spill rays of reflected light upward and outward.

5. In an airport marker light, a casing comprising upper and lower units of substantially the same strength of construction, said lower unit being below the surface of the ground and forming a well, means in said well for supporting an electric lamp with its filament below the surface of the ground, an internal reflector in said well surrounding said lamp and having an open upper end extending to substantially the top of said lower unit and well and concentrating reflected light at a focus above said filament, said upper casing unit comprising an annular flange which forms a base for said upper unit, said upper casing unit also comprising a cover and supporting posts extending down from said cover thereabove, said posts being materially shorter than the distance therebetween, whereby said cover is maintained close to the surface of the ground, rigid light transmitting and refracting means extending from said cover down toward said flange and extending substantially circumferentially from each post to thenext so as to direct light rays around the posts, an external reflector secured to the underside of said cover clear of 'said supporting posts and receiving light from said source and reflector in said well and reflecting it out through said light transmitting means between said posts, and means for securing said flange to said lower unit and thereby securing said units together, said unit securing means being accessible from outside said light transmitting means without removing said cover from said posts, to permit removal of said posts, cover, light transmitting means and external reflector all' intact,

for access to said lamp and internal reflector in said well.

6. In an airport marker light, a casing comprising upper and lower units of substantially the same strength of construction, said lower unit being below the surface of the ground and forming a well, means in said well for supporting an electric lamp with its filament below the surface of the ground, an internal reflector in said well surrounding said lamp and having an open upper end extending to substantially the top of said lower unit and well and concentrating reflected light at a focus above said filament, said upper casing unit comprising an annular flange which forms a base for said upper unit, said upper casing unit also comprising a cover and sup porting posts extending down from said cover to said annular flange and spacing said cover thereabove, said posts being materially shorter than the distance therebetween, whereby said cover is maintained close to the surface of the ground, rigid light transmitting and refracting means extending from said cover down toward said flange and extending substantially circumferentially from each post to the next so as to direct light rays around the posts, an external reflector secured. to the underside of said cover clear of said supporting posts and receiving light from said source and reflector in said well and reflecting it out through said light transmittingmeans be- I f'tween said posts, and means for mounting said reflectors in their respective units and securing said units together to provide a clear passage for direct light from said source to all parts of said external reflector, said unit securing means being accessible from outside said light transmitting means and permitting removal of said posts as a part of said upper unit for access to said lamp and internal reflector.

' 7. In an airport marker light, a casing comprising upper and lower units, said lower unit being below the surface of the ground and forming a well, means in said well for supporting an electric lamp with its filament below the surface of the ground, an internal reflector insaid well surroundingsaid lamp and having an open up-- per end and concentrating reflected light at a focus above said filament, said internal reflector comprising a surface of revolution generated by an ellipse having one focus in the axis of rotation and its major axis at an acute angle thereto, whereby the other focus of the generating ellipse 1 describes a circle, said lamp having a ring filament coinciding with said described circle, said upper casing unit comprising an annular flange which forms a base for said upperunit, said upper casingunit also comprising a cover and supporting posts extending down from said cover to said annular flange and spacing said cover thereabove, said posts being materially shorter than the distance therebetween, whereby said. cover is maintained close to the surface of the ground, light transmitting means extending from said cover down toward said flange and extending subflector all intact, for access to said lamp and internal reflector in said well.

8. In an airport marker light, a casing comprising upper and lower imits of substantially the same strength of construction, said lower unit being below the surface of the ground and forming a well, means in said well for supporting an electric lamp with its filament below the surface of the ground, an internal reflector in said well surrounding said lamp and having an open upper;

end extending to substantially the top of said lower unit and well and concentrating reflected light at a focus above said filament, said upper casing unit comprising an annular flange which forms a base for said upper unit, said upper casing unit also comprising a cover and supporting posts extending down from said cover to said-annular flange and spacing said cover thereabove, said posts being materially shorter than the distance therebetween, whereby said cover is maintained close to the sin'face of the ground, rigid light transmitting means extending from said cover down toward said flange and extending substantially circumferentially from each post to the next, an external reflector secured to the undersideof said cover clear of said supporting. posts and receiving light from said source and reflector in said well and reflecting it out through said light transmitting means between said posts, a

said external reflector having a central part comprising a paraboloidal reflecting surface having its focus at the focus of reflected light from said reflector in said well, said external reflector also having an annular reflecting surface surrounding said paraboloidal surface for reflecting direct rays from said light source downward and outward, and means for mounting said reflectors in their respective units and securing said units together to provide a clear passage for direct.

light from said source to all parts of said external reflector, so that direct light from said filament may reach the annular reflecting surface which surrounds said paraboloidal surface, said unit securing means beingaccessiblefrom outside said light transmitting means and permitting, removal of said posts as a part of said upper unit for access to said-lamp and internal reflector.

I ERNEST M. GLASGOW. 

